1. Field of the Invention
This invention relates to technology for measuring rotation speed of rotating equipment, such as an electric motor.
2. Description of the Related Art
The electric motor disclosed in JP2001-298982A is one example of an electric motor that utilizes permanent magnets and magnet coils.
Conventionally, rotation speed of rotating equipment such as an electric motor is determined by measuring the time required for a single rotation, for example.
However, a problem with this approach is that if rotation speed is slow, a single rotation may take a long time, so that the duration of measurement takes a long time. Another problem is that measurement error depends on the rotation speed; it tends to be low during rotation at high speed.